428 P. Coutts, and H. Weigold. "Organometallic Chemistry of Titanium, Zirconium and Hafnium," Academic Press, New York, N. Y., 1974. Many metallocarboranes exist which have no metallocene counterparts, e.g., [M(CZB&-III)Z]"- (M = Cu, Au; n = 1 or 2), or counterparts that are considerably less stable (M = Ni, Pd, Cr, etc.). For example, see L. F. Warren, Jr., and M. F. Hawthorne, J. Amer. Chem. SOC.,90, 4823 (1968): H. W. Ruhle and M . F. Hawthorne, Inorg. Chem., 7 , 2279 (1968). (a) D. F. Dustin, G. B. Dunks, and M. F. Hawthorne, J. Amer. Chem. SOC.,95, 1109 (1973); (b) W. J. Evans, G. B. Dunks, and M. F. Hawthorne, ibid., 95, 4565 (1973). Satisfactory elemental analyses were obtained for all the new metallocarboranes reported herein. A detailed study of the temperature dependent nmr spectra of these complexes will appear at a later date. CH,CN solution, 0.1 M EtdNPFs, platinum button or hanging mercury drop electrode, sce reference. Under nitrogen or in vacuo, Ill initially dissolved and then rapidly decomposed in acetone to yield a colorless solution: thus it was recrystallized from CH2CI2-THF. D. F. Dustin, W. J. Evans, C. J. Jones, R. J. Wiersema, H. Gong, S. Chan, and M. F. Hawthorne, J. Amer. Chem. SOC.,96, 3085 (1974). Due to coupling of the unpaired electron with 5'V (/ = 'h). R. J. Wiersema and M. F. Hawthorne, J. Amer. Chem. Soc.,96, 761 (1974). For example, the electron-rich metaiiocarboranes containing ds and d9 metals (formally 20- and 21-electron complexes) adopt a "slipped sandwich" structure (cf. R. M. Wing, J. Amer. Chem. SOC., 89, 5599 (1967); 90, 4828 (1968)) while the 15-electron Cr(lil) complexes adopt a symmetric structure containing relatively long metal-to-ring distances (cf. D. St. Clair, A. Zalkin, and D. H. Templeton, Inorg. Chem., 10, 2587 (1971). Also, recent crystallographic studies in these laboratories on the complex (q5-C5H&Fe2C2BsHa have revealed the first ten-vertex metaliocarborane possessing a geometry which cannot be described as a bicapped Archimedean antiprism (K. P. Callahan, W. J. Evans, F. Y. Lo, C. E. Strouse, and M. F. Hawthorne, submitted to J. Amer. Chem. Soc.). This complex formally contains two 17-electron Fe(lll) atoms, thus the entire polyhedron is deficient two electrons. F . Y. Lo, C. E. Strouse, K. P. Callahan, C. B. Knobler and M. F. Hawthorne, J. Amer. Chem. Soc., following communication. For instance, Co(lV), NI(IV), and Cu(lll) are among the highest oxidation states obtainable for these metals, and organometallic complexes in these states would be considered rare although many carboranyi complexes exist. On the other hand, the organometallic chemistry of the early transition metals is dominated by the highest obtainable states ( f 3 , +4), Zr(ll) and Hf(ll) thus being somewhat rare organometallic oxidation states. (14) The C2B10H,22- ligand appears to be a formal 6-electron donor, as in C5H5C~''lC2Bl0Hl2 (see ref 3a and M. R. Churchill and B. G. DeBoer. horg. Chem., 13, 1411 (1974)). Because of the structural similarities between this cobaltacarborane and complex 11, we believe it not unlikely that C2BloH122- is also a 6-electron donor in these early transition metal complexes.
Chris G . Salentine, M. Frederick Hawthorne* Contribution No. 3372, Department of Chemistry University of California Los Angeles, California 90024 Received September 10, 1974
Structures of Metallocarboranes. VI. A Titanium Sandwich Complex. Crystal and Molecular Structure of ~ ~ ~ ~ 3 ~ 4 ~ 1 2 ~ ~ ~ , ~ ' ~ 2 ~ 1 0 ~ 1 0 ~ ~ ~ 3 ~
Bis(tetramethylammonium) 4,4'- commo-Bis(decahydro-l,6-dimethyl-1,6-dicarba4-titana-closo-tridecaborate)(2-) at - 160"' Sir:
The preceding communication2 reported the synthesis and spectral properties of the first metallocarboranes which incorporate group IVa (Ti, Zr) and group Va (V) metals in the polyhedral framework. W e wish to report the crystal and molecular structure of one of these compounds, the bis(tetramethylammonium) salt of the commo titanacarborane anion {4,4'-Ti-[ 1 , ~ - C ~ B , ~ H , O ( C H ~ ) ~ ] * ) ~ - . A well-formed dark red crystal of the compound was mounted on a Syntex P i automated diffractometer equipped with a locally constructed low-temperature device3 and cooled to - 160'. The complex was found t_o crysI tallize in the centrosymmetric triclinic space group P 1 (confirmed by successful refinement) with unit cell dimensions a = 13.412 (3) A, b = 9.325 (2) A, c = 16.781 ( 5 ) A, a = Journal of the American Chemical Society
/ 97.2 /
Table I. Bond Distances in the Metallocarborane Polyhedra" M-C1 M-B2 M-B3 M-C6 M-B7 M-B10 C1-CM1 C1-B2 C1-B3 C1-B5 B2-B5 B2-C6 B2-B9 B3-B5 B3-B7 B3-B8 B5-B8 B5-B9 B5-B11 C6-CM6 C6-B9 C6-BlO C6-Bl2 B7-B8 B7-BlO B7-Bl3 B8-B11 B8-Bl3 B9-B11 B9-Bl2 B10-Bl2 B10-Bl3 Bll-B12 Bll-B13 B12-BI3 a
D
D'
DC
2.176 (5) 2.408 (6) 2.420 (6) 2.471 ( 5 ) 2.433 (6) 2.338 (7) 1.518(7) 1.564 (8) 1.589 (8) 1 ,769 (8) 1 ,990 (9) 1.652 (8) 1.778 (9) 1.995 (9) 1.769 (9) 1.783 (9) 1.918 (9) 1.866 (9) 1 , 8 1 0 (10) 1 . 5 4 6 (7) 1.693 (8) 1.708 (8) 1.710 (8) 1.751 (8) 1.757 (9) 1 ,762 (9) 1.738 (8) 1 ,740 (9) 1 ,732 (9) 1 . 7 4 9 (9) 1 . 7 9 8 (8) 1 ,795 (9) 1.781 (9j 1.786 (9) 1.733 (9)
2.185 ( 5 ) 2.417 (6) 2.406 (7) 2.466 ( 5 ) 2 430 (7) 2.338 (6) 1 ,540 (7) 1.549 (8) 1.561 (8) 1 ,757 (8) 1.992 (5) 1.687 (7) 1.791 (8) 1 ,978 (9) 1 ,773 (8) 1.801 (9) 1 ,909 (9) 1 ,897 (9) 1 ,826 (9) 1.532 (7) 1 ,706 (7) 1 , 7 2 0 (8) 1.713 (8) 1 ,756 (8) 1 ,762 (9) 1.770 (9) 1 ,744 (9) 1 . 7 5 0 (9) 1 ,746 (9) 1.738 (8) 1 . 7 9 8 (9) 1.787 (9) 1.766 (9) 1 . 7 6 9 (9) 1.727 (9)
2.032 (4) 2.199 (6) 2.203 (4) 2.150 (3) 2.165 (3) 2.093 (3) 1.429 ( I O ) 1 ,527 (6) 1 ,775 (6) 2.081 (10) 1 ,694 (7) l.SlS(7) 1 , 9 4 7 (6) 1.813( 5 ) 1.792 ( 5 ) 1.881 (6) 1 ,865 (6) 1.787 (5) 1.686( 5 ) 1.708 (5) 1.665 (4) 1 . 7 8 6 (6) 1.881 (6) 1.785 ( 5 ) 1.741 ( 5 ) 1.770 ( 5 ) 1.733 (6) 1 ,720 (6) I ,802 ( 5 ) 1 . 7 8 3 (6) 1.773( 5 ) 1.789 ( 5 ) 1.788 ( 5 )
D and D' are bond distances in the two independent polyhedra
of the titanium complex and D,are distances obtained by Churchill and DeBoer5 for the cobalt complex.
95.21 ( 2 ) ' , ,6 = 106.15 (2)', and y = 81.55 (2)'. The measured density of l .19 (3) g c m -3at 25' corresponds to a calculated density a t -160' of 1.096 g ~ m - The ~ . unit cell contains two molecules of the acetone-solvated compound [(CH3)4Nl ~ ( T ~ [ C ZOH B II O ( C H ~ ) ~ I ~ ) . ~ ( C H ~ ) ~ C O . A total of 3214 reflections (Mo Ka radiation) with intensities greater than three times their standard deviations were used in the solution and refinement of the structure. Conventional Fourier and least-squares techniques have resulted in R = 0.056, R, = 0.059.4 Full details of the refinement procedure will be discussed in a subsequent manuscript. 2 1 2 ~ ~ I , The compound is comprised of two 13-vertex closed polyhedra fused through the titanium atom, with cations and solvent molecules positioned in sites between the large anions. The geometry of the anion is depicted in Figure 1 , which also indicates the numbering system employed. The observed structure of the 13-vertex polyhedra is similar to that determined by Churchill and DeBoer' in the neutral cobaltacarborane C ~ H ~ C O C ~ Bin ~ that O H the ~ ~ metal atom occupies high-coordinate vertex positions. The Ti-C and Ti-B bonds are much longer than their analogs in the cobalt complex; Ti-C averages 2.18 1 ( 5 ) A (to the lowcoordinate carbon atoms) and 2.468 ( 5 ) A (to the highcoordinate carbon atoms), while Ti-B averages 2.399 (6) A. The overall geometries of the two independent polyhedra a r e identical within experimental error but differ significantly from the cobalt-containing polyhedron (Table I ) . Specifically, extremely long boron-boron bonds between the high-coordinate boron atom 5 and boron atoms 2 and 3 (B5-B2 = 2.081 ( I O ) and B5-B3 = 1.947 (6) A V S . a nor-
January 22, 1975
429
@Ti
‘dB11
Figure 1. Molecular geometry of the titanacarborane dianion
tively, while the titanacarborane and monomeric titanocene are both 14-electron systems. Steric constraints have been postulated to explain the permethyltitan~cene,~.~~ lack of dimerization of [q5-C5(CH3)5]2Ti. This species is only marginally stable and exists in solution in tautomeric equilibrium with the isomeric complex [C5(CH,)s] [C5(CH3)4CH2]TiH; this process involves ring methyl hydrogen abstraction and consequent internal oxidative addition to produce a 16-electron configuration about the metal. A similar electronic configuration is present in the distorted tetrahedral (C~H5)2TiC12.] The titanium atom in the metallocarborane is sandwiched between roughly parallel (dihedral angle between best least-squares planes 6. I ”) six-membered rings and exhibits no significant distortion toward a structure in which the two ligands are “bent back” to present sufficient room for a donor molecule to approach. The long distances between the titanium and the cage atoms would facilitate such a bending without producing unfavorable interactions between hydrogen atoms on the two independent polyhedra, but the molecule shows no inclination to adopt such a configuration. The acetone molecules of solvation present in the crystal a r e distant from the metal center. This compound represents another example of an electron-deficient metallocarborane and shows the largest amount of electron deficiency yet observed. Other crystallographically studied molecules of this type are the ( C ~ B ~‘)2Cr(III) HI monoanion,12 formally a 15-valence electron compound, which exhibits a symmetrical sandwich structure,13 and (CjH5)2Fe2C2B6Hs, which exhibits a large distortion from the idealized polyhedral geometry expected for this ten-vertex system.’ Electron-rich metallocarboranes appear to show a preference for “slipped sandwich” struct u r e ~ , but ’ ~ a t this stage little can be said about any systematic geometric effects of electron deficiency in metallocarboranes.
mal icosahedral B-B distance6 of 1.78 A) were observed in the structure of the cobaltacarborane. This pattern is also observed in the titanacarborane studied here, the average of these two distances being 1.989 (9) A, but the sizable 0.1 34 A difference between the two bonds detected by Churchill and DeBoer is not present here; the maximum difference between the four bonds is 0.017 8, in the titanacarborane. Similarly, the difference in the short B-C distances in the cobaltacarborane (CILB3 = 1.527 (6), C l - B 2 = 1.429 (10) A) is in the case of the titanacarborane much less (CI-B3 = 1.589 (8), 1.561 (8); Cl-B2 = 1.564 (8), 1.549 (8) A). The long B7-BlO bond length of 1.881 (6) A observed in the cobaltacarborane corresponds to boron-boron Acknowledgments. W e wish to thank the Office of Naval distances of 1.757 (9) and 1.762 (9) A in the titanium comResearch and the Army Research Office (Durham) for parplex. In general, the titanacarborane polyhedra show less tial support of this work. Computations were performed a t distortion from “normal” bond distances and less deviation the U C L A Campus Computing Network, whom we thank from a symmetric structure, than does the cobaltacarbofor their generous allocation of computer time. rane. While the metal-carbon and metal-boron bonds in the tiReferences and Notes tanacarborane are considerably longer than those observed in the cobaltacarborane, the coordination geometries in the (1) Part V: K . P. Callahan, W. J. Evans, F. Y. Lo, C. E. Strouse, and M. F. Hawthorne, J. Arner. Chem. Soc., 97, 296 (1975). two complexes are similar. In each case the low-coordinate (2) C. G. Salentine and M. F. Hawthorne, J. Amer. Cbem. Soc., preceding carbon atom. C1, exhibits a short metal-carbon distance, communication, and the boron atom opposite C1 on the six-membered B4C2 ( 3 ) C. E. Strouse, Rev. Sci. Instrm., to be submitted. (4) R = [ Z l l F d - I F d l / Z l F d ] ; R, = [ Z w l I F d - ~ I d l 2 / Z ~ I F d 2 ] ” * . ring, B10, is the next nearest neighbor of the metal. The (5) M. R. Churchill and 8. G. DeBoer, horg. Cbem., 13, 1411 (1974). other four atoms of the B4C2 rings have longer and roughly (6) M. R. Churchill and A. H. Reis, J. Cbem. Soc., Dalton Trans., 1317 equal distances to the metal atom. The five-member boron (1972). (7) R. H. Marvich and H. H. Brintzinger, J. Amer. Cbem. Soc., 93, 2046 rings in the titanium polyhedra are planar within experi(1971); and also J. E. Bercaw. R. H. Marvich, L. G. Bell and H. H. mental error even though long bonds to the high-coordinate Brintzlnger, ibid., 94, 1219 (1972). (8) A. Davison and S. S. Wreford, J. Amer. Cbem. Soc., 96, 3017 (1974). B5 atom result in a large deviation from fivefold symmetry. (9) J. E. Bercaw, R. H. Marvich, L. G. Bell, and H. H. Brintzinger, J. Amer. The coordination geometry of the formally d 2 titaniCbem. Soc., 94, 1219 (1972). um(I1) atom in this compound is of particular interest since (10) J. E. Bercaw, J. Arner. Cbem. SOC.,96, 5087 (1974). (11) V. V. Tkacher and L. 0. Atovmyan, J. Struct. Cbem. USSR, 13, 287 monomeric titanocene, the isoelectronic cyclopentadienyl (1972). analog of this titanacarborane, has not been isolated. A t (12) H. W. Ruhle and M:F. Hawthorne, lnorg. Cbem., 7 , 2279 (1968). (13) D. St. Clair, A. Zalkin, and D. H. Templeton, lnorg. Chem.. 10, 2587 least two compounds with the stoichiometry ( C 1oH 0Ti)2 (1971). have, however, been identified. Marvich and Brintzinger’ (14) R. M. Wing, J. Amer. Cbem. Soc., 89, 5599 (1967); 90,4828 (1968). have characterized a metastable compound to which they Frederick Y. Lo, Charles E. Strouse, Kenneth P. Callahan assign the (( o5-C5Hj)2Ti)2 structure. This compound therCarolyn B. Knobler, M. Frederick Hawthorne* mally rearranges to form a green isomer which has been Contribution No. 3384, Department of Chemistry identified by Davison and Wrefords on the basis of I3C nmr University of California as ~-(~5:~’-fulvalene)-di-~-hydrido-bis(cyc~opentadienyltiLos Angeles, California 90024 tanium). In these two dimeric isomers the titanium atoms achieve 15- and 16-valence electron configurations, respecReceived September 10, 1974 Communications to the Editor
